1. Field of the Invention
The present invention relates to an ultrasonic probe for and a method of acquiring a tomographic image and other graphic images to be taken from the internal organs of a human body by taking advantage of an ultrasound, and more particularly to an ultrasonic probe for and a method of acquiring a tomographic image and other graphic images to be used for the diagnosis by doctors in the hospitals.
2. Description of the Related Art
In recent years, there have been developed and used various kinds of ultrasonic probes which are designed to probe the internal organs of the human body to assist the doctors in diagnosing the human body in the hospitals. Among those ultrasonic probes, there are two types of ultrasonic probes the first one of which is constructed to be moved on while being kept in touch with the human body""s skin to probe the solid internal organs such as livers and pancreas from the outside of the human body, and the second one of which is inserted into the hollow internal organs of the human body including stomachs, rectums and vaginas to probe the hollow internal organs of the human body. Both of the forgoing ultrasonic probes are adapted to emit an ultrasonic wave to the targeted portions of the human body before receiving an ultrasonic wave echoed from the targeted portions of the human body. The ultrasonic wave is transformed by the ultrasonic probe in a conventional manner into an electric signal that is processed into a tomographic image to be displayed on a display unit.
One typical example of the ultrasonic probes is disclosed in Japanese publications such as for example Japanese laid-open publication No. 184532/1991.
The ultrasonic probes herein disclosed are each the second type of the ultrasonic probe and thus provided with a probe unit comprising a transducer for transducing an electric signal into and out of an ultrasonic wave, an electric motor for allowing the transducer to be reciprocally swung around its own axis within a predetermined rotation range, and a reduction gear intervening between the transducer and the electric motor to transmit the rotation torque of the electric motor to the transducer. The transducer is provided in and supported by the housing to be swingable with respect to the housing around the center axis thereof within a predetermined swing rotation range. The transducer is in the form of an arcuate shape and has a space within which the electric motor and the transducer are arranged. The electric motor and the reduction gear are positioned roughly in coaxial relationship with the transducer. The arrangement of the transducer, the electric motor and the reduction gear results in the fact that the transducer is obliged to have a relatively large radius. The large radius of the transducer inevitably makes considerably large its cross-section area taken along a plane perpendicular to the direction in which the transducer is inserted into the internal organ.
As will be understood from the previously mentioned fact, the conventional ultrasonic probe of this type encounters such a problem that the transducer relatively large in radius and cross-section makes the ultrasonic probe unit as a whole to be bulky in size. Further, the fact that the gear of the transducer is drivably meshed with the gear of the electric motor by way of the reduction gear leads to the other problem that these gears thus held in meshing relationship with one another inevitably cause a backlash transmitted to the transducer, thereby deteriorating the accuracy of the ultrasonic probe unit.
It is therefore an object of the present invention to provide an ultrasonic probe that is smaller in size than the conventional ultrasonic probe.
It is another object of the present invention to provide an ultrasonic probe that is higher in accuracy than the conventional ultrasonic probe.
It is a further object of the present invention to provide a method of producing an ultrasonic probe that is smaller in size and higher in accuracy than the conventional ultrasonic probe.
According to one aspect of the present invention, there is provided an ultrasonic probe, comprising: a housing; a driven shaft rotatably supported by the housing; a transducer supported by the driven shaft to be swingable on one side of the driven shaft and operative to transduce an electric signal to and from an ultrasound, the transducer having the ultrasound emitted therefrom and reflected thereto through the housing in a predetermined direction; a drive shaft rotatably supported by the housing, spaced apart from and in parallel relationship with the driven shaft in the predetermined direction; a drive motor supported on the housing and drivably connected to the drive shaft; and a drive belt intervening between the driven shaft and the drive shaft to transmit the rotation from the drive motor to the transducer.
The ultrasonic probe thus constructed can reduce the rotation radius of the transducer independently of the size of the electric motor by having the rotation axes of the drive motor spaced apart from the transducer. This makes it possible to produce an ultrasonic probe small in size. Further, the ultrasonic probe can be high in accuracy as compared with the conventional ultrasonic probe because the rotation of the drive motor is transferred into the rotational motion of the transducer without any gears intervening between the transducer and the drive motor.
The drive belt may be substantially in the form of a loop shape and has rectangular cross section.
The housing of the ultrasonic probe according to the present invention may include an outer case; and an inner case accommodated in the outer case and held stationary with respect to the outer case, the driven shaft being rotatably supported by the inner case; a driven pulley fixedly supported on the driven shaft of the transducer and rotatable together with the driven shaft; and a drive pulley fixedly supported on the drive shaft and rotatable together with the drive shaft, the drive belt being passed on the driven pulley and the drive pulley.
The ultrasonic probe according to the present invention desirably comprises synchronizing means for synchronizing the driven pulley with the drive pulley when the driven pulley is driven to rotate by the drive pulley through the drive belt.
It is desirable that the synchronizing means be constituted by a first projection formed on the driven pulley to radially project from the outer peripheral surface of the driven pulley, a second projection formed on the drive pulley to radially project from the outer peripheral surface of the drive pulley, and the drive belt respectively having first and second holes formed therein in spaced apart relationship with each other in the rotation direction of the drive belt, the first and second holes respectively having the first and second projections received therein to ensure that the drive pulley is driven to rotate in synchronism with the drive pulley.
The synchronizing means makes it possible to produce an ultrasonic probe with no slip causing between the drive belt and the driven and drive pulleys and thus highly responsive and reliable in the torque transmission between the drive and driven pulleys.
The ultrasonic probe according to the present invention may further comprise length adjusting means for adjusting the length of the drive belt with the first pulley and the second pulley to have the first projection and the second projections respectively engaged with first hole and the second hole. In this case, the drive belt has a predetermined length defined by the distance between the first hole and the second hole.
The ultrasonic probe according to the present invention may further comprise an adjusting screw, the drive belt has a first engaging portion held in engagement with the drive pulley, a second engaging portion held in engagement with the driven pulley and a third engaging portion held in engagement with the drive pulley and formed with an adjusting hole having an inner diameter large enough to receive therein the adjusting screw to ensure that the drive belt is adjusted in length under the state that the first engaging portion and the second engaging portion are respectively held in engagement with the drive pulley and the driven pulley.
The length adjusting means is preferably constituted by the adjusting screw, the drive belt, the drive pulley and the driven pulley. The adjusting hole may be in the form of a rectangular shape having a length measured in the longitudinal direction of the drive belt and a width measured in the direction perpendicular to the longitudinal direction of the drive belt. The length of the adjusting hole is necessary to be larger than the width.
The length adjusting means renders it possible to impart tension to the drive belt by puling the extreme end portion of the drive belt. The extreme end portion of the drive belt which falls into being unnecessary after being pulled is cut off from the effective portions of the drive belt. It is therefore possible to provide an ultrasonic probe reduced in manufacturing costs and processes because the fact that the drive belt is in the form of a loop shape.
The drive belt may have an extreme end tab adjacent to the adjusting hole and may be formed with a pair of side notches extending inwardly from the side surfaces of the drive belt between the adjusting hole and the extreme end tab of the drive belt and symmetrically formed with respect to the center line of the drive belt. The drive belt wound onto the drive pulley and the driven pulley is adjusted in length between the drive and driven pulleys with the adjusting hole and the adjusting screw and is imparted a tension by pulling the extreme end tab in the longitudinal direction of the drive belt until the third engaging portion of the drive belt is screwed to the drive pulley.
The ultrasonic probe according to the present invention may further comprise rotation restricting means for restricting the rotation of the drive pulley to within an allowable rotation range.
It is desirable that the drive pulley have a stop projection projecting from one side surface of the drive pulley. In this case, the inner case is formed with a groove receiving therein the stop projection to ensure that the drive pulley is allowed to rotate within the allowable rotation range.
Preferably, the outer diameter of the driven pulley is larger than that of the drive pulley. The load torque of the drive motor and the backlash transmitted to the transducer are therefore reduced, and the drive motor and the drive pulley become smaller.
The rotation of the drive pulley is restricted by the inner case through the stop projection of the drive pulley in the case when the transducer is brought out of the allowable rotational range of the transducer in trouble. It is therefore possible to provide an ultrasonic probe sufficiently reliable by preventing the drive belt from being applied a driving force exceeding the allowable force level.
It is preferred that the ultrasonic probe further comprise tension imparting means for imparting tension to the drive belt. The tension imparting means enables the drive belt to be imparted a constant tension sufficient to drive the transducer without loosening the drive belt and making a vibration noise.
The tension imparting means may comprise a swingable arm having one end portion pivotably supported on the inner case to be swingable with respect to the inner case and the other end portion bent toward the drive belt, an idler roller rotatably supported on the other end portion of the swingable arm in pressing contact with the drive belt, and resilient means for resiliently urging the idler roller into pressing contact with the drive belt to have the drive belt maintained under its tensioned state.
In the preferred ultrasonic probe, the resilient means is constituted by a helical coil spring having one end connected to the longitudinally intermediate portion of the swingable arm and the other end connected to the inner case to ensure that the idler roller is held in pressing contact with the drive belt to have the drive belt maintained under its tensioned state. The drive belt while being driven by the drive pulley is constantly imparted a tension at a tension level applied when the drive belt is assembled with the first and second pulleys.
According to another aspect of the present invention, there is provided a method of producing an ultrasonic probe, comprising the steps of: preparing a driven shaft, a transducer supported by the driven shaft, a drive shaft parallel to the driven shaft and spaced apart from the drive shaft, an adjusting screw and a drive belt having first and second engaging portions, third engaging portion formed with an adjusting hole and an extreme end tab; winding the drive belt onto the drive pulley and the driven pulley to have the first and second engaging portions held in engagement with the drive pulley and the driven pulley; screwing the drive belt to the drive pulley by the adjusting screw through the adjusting hole of the drive belt; imparting the drive belt wound onto the drive pulley and the driven pulley a tension at a predetermined level by pulling the extreme end tab in the longitudinal direction of the drive belt until the third engaging portion of the drive belt is screwed to the drive pulley; and cutting and separating the extreme end tab from the drive belt.
The above series of steps not only make it easy to impart tension to the drive belt but also render it possible to reduce the manufacturing costs and the number of the manufacturing processes of the ultrasonic probe because the drive belt can be tightened without providing additional tension imparting means.